Acceleration sensor

Abstract

A force sensor comprises a substrate having a movable unit which is displaceable in response to one of an applied force and acceleration; an electron emission unit having a cathode for emitting electrons in accordance with an applied potential; an electron absorption unit having an anode for capturing electrons emitted from the cathode, the electron emission unit and the electron absorption unit being formed on a surface of the substrate; and a control unit for, on the basis of the displacement of the movable unit, controlling the electron capturing efficiency of the anode with respect to electrons emitted from the cathode.

What is claimed is: 
     
       1. An acceleration sensor comprising: a substrate having a movable unit which is displaceable in response to acceleration;   an electron emission unit having a cathode for emitting electrons in accordance with an applied potential;   an electron absorption unit having an anode for capturing electrons emitted from said cathode, said electron emission unit and said electron absorption unit being formed on a surface of said substrate;   said movable unit comprising a diaphragm formed by thinning said substrate at a location between said electron emission unit and said electron absorption unit, the diaphragm being deformable by acceleration;   an auxiliary electrode for forming an electric field between said cathode and said anode, said electric field attracting electrons emitted from said cathode to direct the electrons toward said anode;   said diaphragm functioning as a control means for controlling the electron capturing efficiency of said anode with respect to electrons emitted from said cathode, and being displacable to block an electron path from said cathode to said anode, thereby controlling said electron capturing efficiency.   
     
     
       2. A acceleration sensor according to claim 1 having a geometry including X, Y and Z axes, and wherein said cathode of said electron emission unit is located at the center of said movable unit, and said anode of said electron absorption unit comprises a plurality of independent anode units located symetrically around said movable unit on the X and Y axes. 
     
     
       3. A force sensor according to claim 1, having a geometry including X, Y and Z axes, and wherein said anode of said electron absorption unit comprises a plurality of independent anode units on the X and Y axes, said anode units being formed on said movable unit and angularly symmetric in the circumferential direction, and wherein said cathode of said electron emission unit is formed around said movable unit. 
     
     
       4. A force sensor according to claim 2, wherein an anode unit dedicated to the Z-axis is formed at the middle of an anode unit for the X-axis and an anode unit for the Y-axis. 
     
     
       5. A force sensor according to claim 2, wherein said cathode has a comb-like annular shape.